This invention relates to an ultrasonic probe and an ultrasonic scanning instrument capable of bending according to the surface contour of the target body for an ultrasonic visual diagnosis and of thus obtaining an accurate image even from a position close to the body surface.
Although there have been many different kinds of ultrasonic probes for ultrasonic diagnostic apparatus such as a linear type, a convex type and a sector type, the array arrangement of oscillators was always fixed and the direction of ultrasonic wave transmission and reception was also predetermined. FIG. 7 shows a prior art ultrasonic probe l' comprising a series of oscillator pieces 11, 12, 13, . . . above a sound-absorbing material 85, a matching sheet 84 above the oscillator pieces 11, 12, 13, . . . and below an acoustic lens 83 placed against a surface 91 of a target body 9 to be examined. Detection points inside the target body are indicated by symbols (01, 1), (02, 1), . . . (01, 2), . . . (01, N), . . . . To produce such a probe, a piezoelectric ceramic material is attached to a sound-absorbing material 85, and grooves of a constant measurement are cut by a dicing apparatus to produce oscillator pieces. An array of oscillator pieces is thus produced by repeating the process described above. Ultrasonic waves can be transmitted from these oscillator pieces if a voltage is applied from an ultrasonic transmitter circuit to the electrodes (not shown) attached to these oscillator pieces. Ultrasonic waves thus transmitted into the target body 9 are reflected at a position of detection if there is any reflector at the detection position.
As shown schematically in FIG. 8, a prior art ultrasonic diagnostic apparatus using an ultrasonic probe as shown in FIG. 7 may include, in addition to the ultrasonic probe 1', an ultrasonic wave transmitter circuit 2, a receiver circuit 21, an image processing circuit 50, a display device 54 and a control unit 30 for exciting the oscillator pieces of the probe 1' individually and controlling the transmitter circuit 2 to transmit ultrasonic waves to the target body 9 and the receiver circuit 21 to receive through the oscillator pieces reflected ultrasonic waves from detection positions. The control unit 30 may also be adapted to control the image processing circuit 50 such that ultrasonic diagnostic images are displayed on the display device 54.
Assume, for example, that detection position (01, 1) inside the target body 9 shown in FIG. 7 is of interest. For this purpose, five mutually adjacent oscillator pieces 11-15 may be activated at different times such that ultrasonic waves emitted thereby will reach the detection position at the same time. If there is a reflector at this detection position, the reflected waves will reach these oscillator pieces 11-15 with the same time lags with which the waves were transmitted therefrom. These oscillator pieces are adapted to transmit received waves to the receiver circuit 21, which in turn transmits the received signals to the image processing circuit 50. After this series of operations is completed, the next group of five mutually adjacent oscillator pieces 12-16 is caused to similarly transmit ultrasonic waves to determine whether there is a reflector at the corresponding detection position (02, 1). This operation is further repeated such that detection positions at the same depth (scan depth 1) are scanned continuously until the detection position at the farthest right-hand side (with reference to FIG. 7) is scanned. Thereafter, this series of scanning operations is repeated from the group of oscillator pieces at the left-hand corner of the array to scan detection positions at deeper positions (of scan depth 2). By thus repeating this series of processes at different scan depths, it is possible to display a sectional image, say, of a human organ.
FIG. 6A shows a situation where the prior art ultrasonic probe 1' is only lightly contacted to a curved surface of a target body for visual diagnosis. In this situation, the target body is not deformed by the probe, and the waves emitted from the parts not at the center where the probe and the body are not contacting each other must travel through air before reaching the target body and hence are attenuated. Thus, a correct image of a target P may not be obtained in this situation. If the probe is forcibly pressed against the target body, on the other hand, an extended area of the body surface can be directly in contact with the probe, as shown in FIG. 6B, but a target P near the body surface becomes deformed.
With such a prior art probe, accurate images could not be obtained from body parts with large curvatures such as arms and legs because the probe could not completely contact the body surface. If the probe is pressed too hard onto the body surface, portions of the body near the surface are deformed and cannot provide an accurate sectional view. Worse still, this may be painful to the patient being examined. In summary, prior art probes with a fixed array of oscillators could not provide accurate sectional images of body parts near the surface such as the subcutaneous fat and blood vessels.
It is therefore an object of this invention to provide an ultrasonic probe and an ultrasonic scanning instrument using a flexible base plate which can bend according to the curved body surface as shown in FIG. 6C so as to eliminate the problems of prior art technology described above.